Virgin Mobile's latest advertising stunt has been sabotaged by street criminals who have stolen speakers embedded in a special poster site.

The "Respect" advertising campaign uses outdoor posters with real speakers that pump out music near Virgin Mobile shops to attract the attention of passersby.

But the stunt backfired last week when one of the special posters in Enfield, north London, was pinched by thieves.

A spokesman for Virgin Mobile said the company hoped it was not about to become the victim of copycat crimes.

But the company has decided not to dismantle the 49 other poster sites that have been erected across the south-east.

"We like to try and be a bit different and have some fun. It's a shame the Enfield speakers have been stolen and the matter has been reported to the police, but we're not going to pull the campaign," said the spokesman.

And Virgin Mobile's ad agency, Rainey Kelly Campbell Roalfe/Y&R, is planning even more wacky advertising sites featuring anoraks on coatstands. The company hopes they will manage to stay put longer than the speakers.

One-off outdoor advertising sites are becoming more popular as brands seek new and novel ways of reaching customers.

Channel 4 recently put an ice sculpture on display on Cromwell Road in London to promote its most expensive ever drama, Shackleton.

And Mini caused a stir by placing replicas of its new model on the outsides of buildings so it looked like they were being driven up the walls.